This invention relates to self-tightening chucks, particularly as used in textile machines for holding bobbin sleeves during winding or spooling operations and the like. In general, the chuck used for this purpose is a sleeve holding device which is mounted on a rotary, cantilevered shaft projecting outwardly from the side of the machine with stop means to receive the inner end of the sleeve facing the machine side and which has releasable clamping or gripping elements to secure the bobbin sleeve in place.
In recent years, the development of spinning machines for the production of synthetic fibers has led to a very substantial increase in spinning speeds, i.e. the winding speeds required to take up the freshly spun filaments or threads. Because of these rapid winding speeds, e.g. over 3,000 m/min and preferably up to 5,000 m/min or more, considerable time and effort have been spent in attempting to reduce as far as possible the amount of waste thread which accumulates during the necessary exchanges of bobbins or spools, i.e. replacing a full bobbin with an empty bobbin sleeve. In order to reduce the time needed to make this exchange, there have been a number of proposals to provide so-called automatic chucks in the form of sleeve holders which have self-tightening characteristics which permit a substantial reduction in the time needed to remove a full bobbin and insert an empty bobbin sleeve. Although the present state of this art offers a number of different self-tightening chuck or sleeve holder constructions, all of them suffer from various disadvantages.
For example, in the German patent specification (DE-AS) No. 1,038,709, there is described a special chuck or bobbin holder for use in spinning machines for producing synthetic threads wherein frictional gripping contact with the bobbin sleeve is produced by a two-arm rocker lever which is spring-actuated when pushing on the bobbin sleeve so as to press the forward end of the two-armed lever against the inner wall of the sleeve. Centrifugal forces, which occur during the winding, are supposed to reinforce the clamping or gripping action of this chuck. Due to the large number of pivot positions required and the open construction of this mechanism, the chuck is unusually subject to fouling and is therefore difficult to operate and maintain under typical working conditions. Moreover, in order to avoid deformation of the bobbin sleeve caused by the point-like pressure of the gripping positions on the sleeve circumference, the contact pressure of each position must be reduced to a value which no longer guarantees the secure holding of the bobbin, especially in handling large and relatively heavy windings.
In a sleeve coupling for twist spindles disclosed by the German patent specification (DE-AS) No. 1,061,242, a rubber ring is used to achieve a frictional locking connection between the sleeve holder and the bobbin sleeve. In its relaxed position, the rubber ring is free of contact with the inner wall of the sleeve, but with the aid of several gripping elements which are pivoted to swing outwardly to the circumference of the holder, the rubber rings are distended or stretched outwardly to make contact with the inner wall of the sleeve. During operation of this spindle, centrifugal forces also act outwardly to stretch the rubber rings and bring them into gripping contact with the sleeve. The greatest disadvantage of this particular sleeve couplings resides in the fact that the sleeve is firmly gripped only at high rotational speeds. At lower speeds or at rest, the bobbin sleeve sits loosely on the spindle and a firm gripping action is not possible, thereby causing problems in unloading the full bobbin and inserting an empty sleeve. Besides, this device permits only a pointwise bracing or gripping of the sleeve which causes deformation of the sleeve wall.
Another winding mandrel with an automatic chucking feature is disclosed in U.S. Pat. No. 3,495,781, corresponding to DE-AS No. 1,574,399, wherein the bobbin sleeve is secured in position with the aid of two rubber rings. This is a very expensive construction, requiring in each case a hydraulic or pneumatic chucking device and braking device. The release of the full bobbin and the clamping of the empty bobbin sleeve occur automatically in lifting off the bobbin from the drive roller or in adding on the empty sleeve. Such devices tend to suffer from frequent mechanical failures which cannot be anticipated or prevented by normal maintenance of the machinery.
A recent chuck assembly for textile bobbins is disclosed in U.S. Pat. No. 4,202,507, issued May 13, 1980, wherein the problems in this art are to be solved by using two rubber O-rings, one at the inboard end and the other at the outboard end of the chuck, the inboard O-ring actuating the outboard O-ring over a set of two-armed levers, the two O-rings being pressed between the inner surface of the sleeve and a circumferentially grooved segment of the chuck shaft. The use of mechanical levers set into the chuck shaft is still relatively complicated and is subject to fouling as well as general maintenance problems.